I don't know how true that is. Look at the past couple MLS Cup winners for example;
2017: Jozy, Bradley, Seba
2018: Barco, Almiron, Martinez
2019: Ruidiaz, Lodiero, Arreaga + Morris & Roldan
2020; Zardes, Zelarayan, Nagbe
2021: Moralez, Castellanos, Moreno, Magno
All these teams had heavy investment and reliance on their DP's and the top couple scorers after that. After that they relied on a mix of MLS vets and strong youth to fill out the roster. The most balance winners I can think of in recent years are probably Sporting (2013), Seattle (2016),
Having game-breaking talent on your team in MLS goes a long way. I think it's better than being a more balanced team.